This invention relates to a thickness standard sample applicable to calibration of a thickness gauge using fluorescent X-ray or other radiant rays.
Prior thickness standard samples are formed with thin films electroplated or coated on base plates. These films are, for instance, 300 grams/m.sup.2 of zinc in thickness and have thickness fluctuation of .+-.50 to 80 grams/m.sup.2 in range in a sample of 100 mm.times.200 mm surface area.
Because of this uneveness of the film thickness, they are not suitable for accurate calibration of industrial gauges such as X-ray thickness gauges.